SAN ANTONIO — Something was up when Miami Heat coach Erik Spoelstra subbed out superstar LeBron James with 7:03 left in the third quarter.

James normally plays for a longer stretch at the start of second half. But with the air conditioning on the fritz turning the AT&T Center into an uncomfortable sauna and James' history of cramping in similar arena conditions, the move foreshadowed what would happen later.

James was in and out of the game with severe cramps in his left leg and did not play the final 3 minutes, 59 seconds in Miami's 110-95 loss to the San Antonio Spurs.

"It's frustration and anger," said James who played 32:53, nearly seven minutes fewer than he normally has played in this postseason not counting his foul-plagued Game 5 against the Indiana Pacers in the Eastern Conference finals.

James walked out of the arena surrounded by security and a Nike executive, and this story line will dominate the next two days — until, and perhaps even during, Game 2 Sunday night in San Antonio.

Following the game, news reporters crowded James' cubicle in the Heat locker room, but a Heat media relations official said it was not known how long James would receive treatment, which included intravenous fluids.

"I'm feeling better than I did when I came off the floor," James told a pool reporter, the only one allowed to interview him. "So, doing better."

James said he wanted to return to the game, but Spoelstra shot down that plan. He left for good shortly after a driving layup cut the Spurs' lead to 92-90 with 4:09 remaining. He failed to make it back down the court following the shot and was carried off the floor by his teammates. Miami faltered without him in the final minutes.

"I was going to try to give it a go and Spo said, 'No,' " James said. "It sucks at this point in time in the season."

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Heat trainers did what they could, including leg massages and ice treatment, and that staff will be under pressure to prevent James from cramping in Game 2.

The conspiracy theorists will put on their tin-foil caps and try to claim subterfuge by Spurs. Spoelstra shot down that idea, too.

"No, that would take an incredible mind to try to plan that for both teams to be able to go through that," he said. "Both teams are trying to manage it the best you could. We were going deeper into our subs, quicker subs than you're used to seeing."

But the conspiracy theorists weren't the only ones out in full force. The Internet trolls, from Spurs fans to ESPN pundits to Gatorade, had a field day mocking James.

I don&#39;t want to hear any excuses about LeBron cramping. Both teams played in same heat. Nobody kept LeBron from drinking more water.

"Cramps are involuntary and often violent contraction of a muscle," athletic trainer Jeff Stotts told USA TODAY Sports in an e-mail early Friday morning.

James was likely experiencing what is known as a tonic spasm in which the muscle contraction is unrelenting and the player is unable to get it to relax.

"Overexertion, fatigue and an excessive loss of fluids and electrolytes can all cause cramps to occur," Stotts said. "In LeBron's case it was probably a combination of all or some of these factors. For a player with his body type, the associated pain and limitation was likely considerable."

This isn't the first time cramps limited James. In Game 4 of the 2012 Finals against the Oklahoma City Thunder, James had to sit because of cramps. But he returned, made a big three-pointer late in the game and helped the Heat take a 3-1 series lead.

Stotts, who tracks player injuries, said James also cramped up at least three other times. Preventative maintenance, he said, is the best way to avoid cramps.

"Players (who) go into a game knowing the temperature will be higher than normal will load up on electrolytes and additional fluids to insure their bodies are better prepared," Stotts said. "LeBron and the Heat, and San Antonio as well, didn't have that privilege.

"However once a player begins to experience a cramp, it can hopefully be managed by relaxing the area. Gentle massage and mild, steady stretching often help. Applying ice or even ice massage can also reduce the spasms. Moving forward the Heat will likely force fluids and take the necessary steps to make sure he's not only re-hydrated but his mineral and electrolyte levels are back where they should be."

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James said he drank the normal amount of fluids before Game 1.

"I got all the fluids I need to get. I do my normal routine I've done and it was inevitable for me tonight, throughout the conditions out there on the floor," James said. "I lost all the fluids that I was putting in in the last couple of days out there on the floor.

"Drank a lot at halftime, even changed my uniform, just tried to get the sweat up off of you. Our training staff tried to do the best they could by giving us ice bags and cold towels on timeouts, keep us dry. It was an unusual circumstance. I never played in a building like that."

"They moved the ball extremely well. I think they had 30 assists," said James, who had perused the box score.

The good news for the Heat: The air conditioning is expected to be fixed by the start of Game 2, and James has two full days of rest.

"I need it, I need it, I need it," James said. "We're going to start tonight, continue to get the fluids in me and get me ready for Sunday. Thankful for the fact that I can get on it tonight, and put myself in a position where I can be out there for my team for the long haul. And sitting on the sideline — if I'm not in foul trouble — is not good for us and not good for me. Look forward to Game 2 and go from there."

Jeff Zillgitt is an NBA insider for USA TODAY Sports. Follow him on Twitter at @JeffZillgitt.

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8. Everyone's an X factor. Both the Heat and Spurs fill their benches (and even starting lineups) with players who can take over occasionally or make nary a peep. Rashard Lewis, Chris Andersen (right), Norris Cole and others could give the Heat major lifts for a game or two, while Boris Diaw (left), Marco Belinelli and Patty Mills are lead candidates to fill 2013 hero Danny Green's role for the Spurs. Steve Mitchell, USA TODAY Sports

7. Hot Heat from three. Miami loves to spread the floor using LeBron James and Dwyane Wade's penetration, which then means open three-pointers as defenses collapse. Will the Spurs be smart and stay at bay on hot shooters such as Ray Allen (pictured) and Shane Battier? Steve Mitchell, USA TODAY Sports

6. Retirement. Heat forward Shane Battier is joining ESPN's college basketball coverage after the season. Spurs star Tim Duncan can opt out of his contract and walk off into the sunset. Heat guard Ray Allen is a free agent and may walk away from a Hall of Fame career. Those guys and others (Matt Bonner? Udonis Haslem?) can throw everything they have into this series and be difference-makers. Steve Mitchell, USA TODAY Sports

5. Manu's revenge. Spurs sixth man Manu Ginobili took last season's loss very, very hard. He was the goat in the blown lead of Game 6, which would have given the Spurs their fifth championship and Ginobili his fourth. But he has been revitalized this season and particularly played well in the Western Conference finals. Soobum Im, USA TODAY Sports

4. Dominant Dwyane Wade? The Heat guard was Finals MVP back in 2006, but knees have limited his playing time and explosiveness. Still, he has looked better this postseason than he has in two years. He's averaging 20.2 points on 54.0% shooting in his last nine games. If Wade's at full force, the Heat aren't going to lose. Steve Mitchell, USA TODAY Sports

3. Gregg Popovich, basketball savant. With all respect to the Heat's Erik Spoelstra, Popovich tops every list of the best current NBA coaches for a reason. He thrives in tight spaces, making major lineup switches at a moment's notice and pulling them off flawlessly. Popovich tirelessly prepares his players for any situation and loves to put them in mismatches to cause havoc for less-prepared opponents. Soobum Im, USA TODAY Sports

2. Tony Parker's ankle. The Spurs point guard hobbled through last season's Finals and now again has a sprained left ankle. Quickness is essential to Parker's penetration, and if he can't get to the basket, the Spurs won't as easily stretch the Heat's defense. Parker probably is the Spurs' best player when healthy. What will he have to offer? Soobum Im, USA TODAY Sports

1. LeBron being LeBron. The NBA MVP is no longer his, but the title of best player in the world still belongs to LeBron James. He has carried the Heat to these past two titles but can hit free agency this offseason. A three-peat could both convince him to stay and be the perfect note to walk out on. The Spurs do a great job of neutralizing star opponents, but James is sure to blow up at least once or twice. If he can do it four times, the Heat will take that third consecutive championship. Steve Mitchell, USA TODAY Sports